Thermal Energy

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Transcript of Thermal Energy

Thermal EnergyTemperature and Heat-Heat Transfer-Thermal ExpansionIdeal GasesEqual to Boltzmann's Constant times Avogadro's number Boltzmann's Constant=1.38x10^23 J/KAvogadro's number=the number of basic particles per mole of a substance NA=6.0221415 × 1023

Atomic Model of GasPV Diagrams Represents ideal gas processesEach point represents a single unique state of gasConstant Volume, Vf=ViRepresented as a vertical lineIsobaric Processes= constant pressure, Pf=PiRepresented as a horizontal lineIsothermal Processes= constant temperature, Tf=TiRepresented as a hyperbola due to the inverse relationship between pressure and volumeAdiabatic=an instant change in pressure with no time to change heat Laws of ThermodynamicsFirst Law and Second LawEntropyThe Carnot CycleAmanda Hymer, Katie Darrah, and Samantha Caramico.ProcessesIdeal gas- gas where all collisions between atoms and molecules are perfectly elasticIdeal gas law- PV=nRTP=pressureV=volumen=number of molesR=ideal gas constant (8.314 J·K−1·mol−1)T= temperature in kelvinsIdeal Gas ConstantThermal Energy is equal to the total kinetic energy of the moving atoms in gasTemperature is a measure of average kinetic energymeasured in kelvins T(K)=T(C)+273Kavg=(3/2)KBTKB=Boltzmann's Constant 1.38x10^23 J/KThermal energy of an ideal gas with N atoms is equal to the sum of kinetic energyEth=NKavg=(3/2)NKBTThermal Energy id directly proportional to temperatureEnergy of Ideal GasKinetic Theory= a theory that describes physical properties in terms of motion in atoms and molecules, such as pressure and volumeMolecules in a sample have different speedsThe average speed is called root mean square (rms)Vrms=√(3Kb/T)Ideal Gas ProcessesProperties:Quantity is fixedDefined initial state of pressure, volume and temperatureDefined final state of pressure, volume and temperatureNumber of moles and molecules does not change in a sealed container(PiVi)/Tf=(PfVf)/TfFirst Law: when only the thermal energy changes Eth= W + QEth= thermal energy; W= work (J); Q= heat (J)Second Law: the entropy of an isolated system always increases until equilibrium is reachedheat energy spontaneously flows only from hot to coldthe energy transformation is irreversibleno heat engine can be 100% efficient-Mechanical Equivalent of Heat.

-Methods of Heat Transfer-occurs when energy is transferred into or out of something, caused by differences in temperature. A measure of the degree of disorder in a system, and this always increases because no system is perfectIsovolumetric: a gas process with an unchanging volume. So W=0 and V=0 Eth=QIsobaric: a gas process that occurs with an unchanging pressure. So p=0 and W= -p V Eth= Q + (-p V)Isothermal: a gas process that occurs with an unchanging temperature. So T=0 and Eth=0Q=-WAdiabatic: a gas process that occurs when heat is not transferred. So Q=0 in this case. Eth= W-the amount of heat energy depends on three quantities-change in temperature: T-mass: m-heat capacity: c Q=cm T

-most substances change in size once applied to a change in temperature*increase in temperature= expansion*decrease in temperature= contracts-temperature is the measure of how much internal energy a substance contains.

-Example: With an increase in heat, the metal plate will increase. The hole in the center will expand instead of getting smaller.Heat Enginetakes thermal energy and converts it to other formsefficiency is described as how much useful work is output for a given amount of heat energy inputemax=1- (Tc/Th)The Carnot Cycle is the most efficient engine possibleFormula: J=W/Q-Amount of work required to raise the temperature of a substance of unit mass by one degree Kelvin.-Constant through natureExample:An iron ball is dropped onto the pavement from a height of 100 m. If half of the heat generated goes into warming the ball, find the temperature increase of the ball. (The specific heat capacity of iron is 450J/((kg)(degrees Celsius)) Q=mgh2_____; Q=cm T_____mgh2=cm TT=gh___2c=______________(9.81m/s )(100m)2